1. Technical Field
The present invention relates to an image forming apparatus using an electrophotographic developing process, and more particularly, relates to a method for processing paper jam error upon occurrence of paper jam in an image forming apparatus.
2. Related Art
Electrophotographic developing processes are widely used in computer printers, facsimile machines and photocopiers in order to produce images on recording media in response to video signals. A common example of an electrophotographic printing apparatus is a laser beam printer which prints images on individual sheets of paper through a series of electrostatic image-forming steps. Generally, the process of electrostatic image forming includes charging a photosensitive drum to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photosensitive drum is exposed to a light image to record an electrostatic latent image on its surface. The latent image is then developed by applying toner from a developing unit onto the photosensitive drum which is subsequently transferred and fixed on a recording medium. When a toner image is fixed on a recording medium, the toner image is first heated and fused onto the recording medium, and then naturally cooled so that it is fixed onto the recording medium.
A significant problem that frequently occur in such an image forming apparatus is the "paper jam." Paper jams occur mainly due to paper feed failure, state damage of printing papers, jamming or sliding the papers in a specific portion of a paper conveyance path, and trouble of assemblies disposed in the paper conveyance path. Generally, when a paper jam error occurs, the image forming apparatus detects the paper jam error, and then processes the detected paper jam error by stopping the current printing operation and informing a user of occurrence of the paper jam error with visual message and an auditory message. Examples of conventional jam detection and recovery schemes are disclosed in U.S. Pat. No. 4,395,111 for Sheet Conveying Device issued to Takahashi et al., U.S. Pat No. 4,878,087 for Image Forming Apparatus With Jam Removal Mechanism issued to Sakai et al., U.S. Pat. No. 4,878,428 for Control Method Of Transporting A Cut Sheet In A Printing Station And An Apparatus Using The Same issued to Watarai, U.S. Pat. No. 4,970,599 for Image Processing Apparatus With Plural Page Memory And Error Detection issued to Nobuta, U.S. Pat. No. 5,030,991 for Jam Detection And Clearance System For Duplex Copiers issued to Zaitsu et al., U.S. Pat. No. 5,081,490 for Method Of Controlling Image Forming Apparatus When A Jam Occurs In The Original Feeder issued to Wakao, U.S. Pat. No. 5,117,261 for Image Forming Apparatus With Jam Recovery Function issued to Sakai et al., and U.S. Pat. No. 5,311,254 for Image Forming Apparatus Having Paper Jam Detecting System For The Automatic Document Handler issued to Watanabe.
Recent efforts to eliminate paper jams from an image forming device by employees of the assignee of this instant application are disclosed in U.S. Pat. No. 5,459,553 for Method For Eliminating A Paper Jam In An Image Forming System issued to Kim, U.S. Pat. No. 5,461,460 for Method For Eliminating A Paper Jam In An Image Forming System issued to Lee, and U.S. Pat. No. 5,534,976 for Method For Eliminating A Paper Jam Of An Image Forming System And Apparatus Therefor issued to Kim.
Paper jam error is generally classified with three categories depending on where the paper jam error is generated, e.g. the feeding and conveying of paper, or the transferring of paper, or the fixing and discharging of paper. A first error is generated upon feeding the paper, a second error is generated upon transferring the papers, and a third error is generated upon fixing and discharging the papers. Hereinafter, for the sake of clarity, the first error is referred to as "jam 0", the second error "jam 1", and the third error "jam 2". Among the paper jam errors, the jam "0" is generated by paper feed failure when the papers are not normally fed or conveyed from a paper cassette into an image forming device. Usually, the paper feed failure occurs when paper is not picked up from the paper cassette.
When jam "0" of the paper jam error is generated during consecutive printing operations, the image forming apparatus still performs the previous printing operation. In this situation, the typical image forming apparatus processes the paper jam error, and as a result, even the previous printing operation is interrupted. Here, the consecutive printing operations are performed and the previous printing paper is referred to as a paper preceding a paper to be fed currently. Typically, during the consecutive printing operations, the image forming apparatus feeds a next paper before the preceding paper is wholly discharged, so that in case of a jam "0", the printing operation on the previous printing paper can not be completed. Therefore, the user must reprint not only the paper where the paper jam error occurs but also the preceding paper before the current paper to be fed for the current image formation.
When paper becomes jammed due to a paper feed failure while the image forming apparatus performs the previous printing operation, it is my observation that the user must reprint the paper to be fed currently as well as the previously albeit defectively printed paper by immediately processing the generated paper jam error. This reprint requirement is not only undesirable but unnecessarily consumes papers.